Abstract: A system includes a plurality of thermostats corresponding to a plurality of HVAC systems that serve a plurality of spaces and a computing system communicable with the plurality of thermostats via a network. The computing system is configured to, for each space of the plurality of spaces, obtain a set of training data relating to thermal behavior of the space, identify a model of thermal behavior of the space based on the set of training data, perform a model predictive control process using the model of thermal behavior of the space to obtain a temperature setpoint for the space, and provide the temperature setpoint to the thermostat corresponding to the HVAC system serving the space. The plurality of thermostats are configured to control the plurality of HVAC systems in accordance with the temperature setpoints.

Abstract: A thermostat for a building zone includes at least one of a model predictive controller and an equipment controller. The model predictive controller is configured to obtain a cost function that accounts for a cost of operating HVAC equipment during each of a plurality of time steps, use a predictive model to predict a temperature of the building zone during each of the plurality of time steps, and generate temperature setpoints for the building zone for each of the plurality of time steps by optimizing the cost function subject to a constraint on the predicted temperature. The equipment controller is configured to receive the temperature setpoints generated by the model predictive controller and drive the temperature of the building zone toward the temperature setpoints during each of the plurality of time steps by operating the HVAC equipment to provide heating or cooling to the building zone.

Abstract: An actuator for controlling a flow regulation device. The actuator includes a drive device coupled to the flow regulation device and a motor coupled to the drive device and operable to move the drive device. The actuator further includes a processing circuit configured to receive a first measurement of a characteristic, control the actuator to reposition the flow regulation device in a first direction, receive a second measurement of the characteristic, determine an installation error associated with at least one of the actuator and the flow regulation device based on the first measurement and the second measurement.

Abstract: A system for controlling flow of a fluid through a heat exchanger in a heating, ventilation, or air conditioning (HVAC) system includes a flow control device operable to adjust the flow of the fluid through the heat exchanger, temperature sensors positioned to obtain a temperature differential of the fluid across the heat exchanger, and a controller configured to compare the temperature differential to a threshold. Responsive to the temperature differential being less than the threshold, the controller is configured to calculate an adjusted setpoint for the flow control device as a function of both the temperature differential and the threshold and operate the flow control device to adjust the flow of the fluid through the heat exchanger in accordance with the adjusted setpoint.

Abstract: A thermostat for a building zone includes at least one of a model predictive controller and an equipment controller. The model predictive controller is configured to obtain a cost function that accounts for a cost of operating HVAC equipment during each of a plurality of time steps, use a predictive model to predict a temperature of the building zone during each of the plurality of time steps, and generate temperature setpoints for the building zone for each of the plurality of time steps by optimizing the cost function subject to a constraint on the predicted temperature. The equipment controller is configured to receive the temperature setpoints generated by the model predictive controller and drive the temperature of the building zone toward the temperature setpoints during each of the plurality of time steps by operating the HVAC equipment to provide heating or cooling to the building zone.

Abstract: A method for calibrating a flow sensor in a heating, ventilation, or air conditioning (HVAC) system. The method includes receiving, at a controller, a request to enter a calibration mode and, in response to receiving the request, automatically commanding a flow control device to achieve a target flow rate. The method further includes generating, by the controller, calibration data for the flow sensor using a reference flow value of the flow rate when the flow control device has achieved the target flow rate and a corresponding flow measurement from the flow sensor.

Abstract: An adaptive flow limit controller for controlling a flow rate of a fluid through a heat exchanger includes a processing circuit. The processing circuit is configured to use an adaptive model to determine a threshold flow rate of the fluid through the heat exchanger at which a gradient of a temperature difference of the fluid across the heat exchanger with respect to the flow rate of the fluid through the heat exchanger has a threshold gradient value. The processing circuit is configured to operate a flow control device to maintain the flow rate of the fluid of through the heat exchanger at less than or equal to the threshold flow rate.

Abstract: A freeze protection system for a heating, ventilation, or air conditioning (HVAC) system is shown. The freeze protection system includes a temperature sensor positioned at an inlet of a coil within which a liquid is at risk of freezing, and a controller comprising a processor and memory. The memory stores instructions that are executed by the processor. The processor is instructed to obtain a measured temperature of the liquid at the inlet of the coil from the temperature sensor, compare the measured temperature of the liquid at the inlet of the coil with a freeze prevention temperature threshold, engage a freeze prevention action in response to a determination that the measured temperature of the liquid at the inlet of the coil is less than or equal to the freeze prevention temperature threshold.

Abstract: A system for controlling a flow rate of a fluid through a valve is provided. The system includes a valve and an actuator. The actuator includes a motor and a drive device that is coupled to the valve for driving the valve between multiple positions. The system further includes a flow rate sensor and a controller that is communicably coupled with the flow rate sensor and the motor. The controller is configured to receive a first flow rate setpoint, determine a first actuator position setpoint using a proportional variable deadband control technique based on the first flow rate setpoint and a flow rate measurement, and receive a second flow rate setpoint. In response to a determination that certain low flow criteria are satisfied, the controller is configured to determine a second actuator position setpoint using the proportional variable deadband control technique based on a low flow compensation setpoint.

Abstract: A freeze protection system for a heating, ventilation, or air conditioning (HVAC) system is shown. The freeze protection system includes a temperature sensor positioned at an inlet of a coil within which a liquid is at risk of freezing, and a controller comprising a processor and memory. The memory stores instructions that are executed by the processor. The processor is instructed to obtain a measured temperature of the liquid at the inlet of the coil from the temperature sensor, compare the measured temperature of the liquid at the inlet of the coil with a freeze prevention temperature threshold, engage a freeze prevention action in response to a determination that the measured temperature of the liquid at the inlet of the coil is less than or equal to the freeze prevention temperature threshold.

Abstract: A system includes a plurality of thermostats corresponding to a plurality of HVAC systems that serve a plurality of spaces and a computing system communicable with the plurality of thermostats via a network. The computing system is configured to, for each space of the plurality of spaces, obtain a set of training data relating to thermal behavior of the space, identify a model of thermal behavior of the space based on the set of training data, perform a model predictive control process using the model of thermal behavior of the space to obtain a temperature setpoint for the space, and provide the temperature setpoint to the thermostat corresponding to the HVAC system serving the space. The plurality of thermostats are configured to control the plurality of HVAC systems in accordance with the temperature setpoints.

Abstract: A system for controlling a flow rate of a fluid through a valve is provided. The system includes a valve and an actuator. An actuator drive device is driven by an actuator motor and is coupled to the valve for driving the valve between multiple positions. The system further includes a differential pressure sensor configured to measure a differential pressure across the valve and a controller that is communicably coupled with the differential pressure sensor and the motor. The controller is configured to receive a flow rate setpoint and the differential pressure measurement, determine an estimated flow rate based on the differential pressure measurement, determine an actuator position setpoint using the flow rate setpoint and the estimated flow rate, and operate the motor to drive the drive device to the actuator position setpoint.

Abstract: A system includes a plurality of thermostats corresponding to a plurality of HVAC systems that serve a plurality of spaces and a computing system communicable with the plurality of thermostats via a network. The computing system is configured to, for each space of the plurality of spaces, obtain a set of training data relating to thermal behavior of the space, identify a model of thermal behavior of the space based on the set of training data, perform a model predictive control process using the model of thermal behavior of the space to obtain a temperature setpoint for the space, and provide the temperature setpoint to the thermostat corresponding to the HVAC system serving the space. The plurality of thermostats are configured to control the plurality of HVAC systems in accordance with the temperature setpoints.

Abstract: A system for controlling flow of a fluid through a heat exchanger in a heating, ventilation, or air conditioning (HVAC) system includes a flow control device operable to adjust the flow of the fluid through the heat exchanger, temperature sensors positioned to obtain a temperature differential of the fluid across the heat exchanger, and a controller configured to compare the temperature differential to a threshold. Responsive to the temperature differential being less than the threshold, the controller is configured to calculate an adjusted setpoint for the flow control device as a function of both the temperature differential and the threshold and operate the flow control device to adjust the flow of the fluid through the heat exchanger in accordance with the adjusted setpoint.

Abstract: An actuator for controlling a flow regulation device. The actuator includes a drive device coupled to the flow regulation device and a motor coupled to the drive device and operable to move the drive device. The actuator further includes a processing circuit configured to receive a first measurement of a characteristic, control the actuator to reposition the flow regulation device in a first direction, receive a second measurement of the characteristic, determine an installation error associated with at least one of the actuator and the flow regulation device based on the first measurement and the second measurement.

Abstract: A method for controlling flow in a heating, ventilation, and air conditioning (HVAC) system includes adjusting a setpoint associated with a valve based on a temperature change across a heating or cooling coil to reduce energy waste. The method includes receiving a first temperature measurement associated with an inlet of the coil, receiving a second temperature measurement associated with an outlet of the coil, calculating a difference between the first temperature measurement and the second temperature measurement, determining that the difference between the first temperature measurement and the second temperature measurement is below a threshold, and adjusting a setpoint associated with the valve. Additional control features may be provided to improve system behavior such as a pulse generation feature, a change-limiting feature, and a reevaluation feature.

Abstract: A method for controlling flow in a heating, ventilation, and air conditioning (HVAC) system that imposes an upper limit on the flow of fluid through a heating or cooling coil. Imposing this limit on the flow rate ensures that a temperature change across the coil remains above a minimum threshold and can significantly reduce energy waste. The method includes receiving a first temperature measurement associated with an inlet of the coil, receiving a second temperature measurement associated with an outlet of the coil, and receiving a flow measurement associated with the valve, applying the first temperature measurement, the second temperature measurement, and the flow measurement as input to a model, determining a maximum flow rate that ensures that a difference between the first temperature measurement and the second temperature measurement is above a threshold using the model, and operating the valve in accordance with the maximum flow rate.

Abstract: A system for controlling a flow rate of a fluid through a valve is provided. The system includes a valve and an actuator. An actuator drive device is driven by an actuator motor and is coupled to the valve for driving the valve between multiple positions. The system further includes a flow rate sensor configured to measure the flow rate of the fluid through the valve and a controller that is communicably coupled with the flow rate sensor. The controller is configured to receive a flow rate measurement from the flow rate sensor, adjust a control deadband based on an actuator command history, and determine a compensated position setpoint using the flow rate measurement, the adjusted control deadband, and a proportional variable deadband control technique. The controller is further configured to operate the motor to drive the drive device to the compensated actuator position setpoint.

Abstract: An adaptive flow limit controller for controlling a flow rate of a fluid through a heat exchanger includes a processing circuit. The processing circuit is configured to use an adaptive model to determine a threshold flow rate of the fluid through the heat exchanger at which a gradient of a temperature difference of the fluid across the heat exchanger with respect to the flow rate of the fluid through the heat exchanger has a threshold gradient value. The processing circuit is configured to operate a flow control device to maintain the flow rate of the fluid of through the heat exchanger at less than or equal to the threshold flow rate.

Abstract: A method for calibrating a flow sensor in a heating, ventilation, or air conditioning (HVAC) system. The method includes receiving, at a controller, a request to enter a calibration mode and, in response to receiving the request, automatically commanding a flow control device to achieve a target flow rate. The method further includes generating, by the controller, calibration data for the flow sensor using a reference flow value of the flow rate when the flow control device has achieved the target flow rate and a corresponding flow measurement from the flow sensor.